Telephone system



CALL/N6 Filed Feb. 12, 1932 FIG.

L.'B. HAIGH ET AL -TELEPHONE SYSTEM 7 Sheets-Sheet 1 'NVENTORS H. 5 A. BORZER BVWWM A T TnP/VEY Oct. 4, 1932. L. B. HAIGH ET AL TELEPHONE SYSTEM 7 Sheets-Sheet 2 Filed Feb. 12., 1932 INVENTORS 5- HA/GH H E A. BORZER ATZORNEY L. B. HAIGH ET AL TELEPHONE SYSTEM Oct. 4, 1932.

Filed Feb. 12. 1932 7 Sheets-Sheet 3 B. HA IGH BVWWM ATTORNEY Oct. 4, 1932. HAIGH ET AL 1,881,273

TELEPHONE SYSTEM Filed Feb. 12 1952 7 Sheets-Sheet 4 FIG. 4

L. B. HA/GH MEMO H. 1: A. BORZER MWW ATTORNEY Oct. 4-, 1932. HAIGH ET AL 1,881,273

TELEPHONE SYSTEM Filed Feb. 12, 1952' "I Sheets-Sheet 5 L. B. HA/GH INVENTORSH 5 A. BORZER BVWW A T TORNEY ll) Q.

' n i- 1; E0

TELEPHONE SYSTEM Filed Feb. 12, 1932 7 Sheets-Sheet 6 FIGSA L. B. HA/GH INVENTORSH. E. A. BORZER A 7' TOPNE v Oct. 4, 1932. l... B. HAIGH ET AL TELEPHONE SYSTEM Filed Feb. 12, 1932 '7 Sheets-Sheet 7 m&

Fatentcd @ct. 4, 1932 'rricE .7 Arie I LESLIE H'AIGI-I AND HENRI E. A. BORZER, O1 PARIS, FRANCE, ASSIGNORS TO WEST- ERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK TELEPHONE SYSTEM Application filed February 12, 1932, Serial No.

This invention relates to telephone systems of the automatic or semi-automatic type and particularly to telephone systems comprising a plurality of different exchanges.

It is an object ofthe invention'to provide improved arrangements for establishing connections between subscribers located in different exchanges of the network.

In order to provide an efficient system for interworlring between exchanges which may be separated by long distances alternating currents are employed for signaling between such exchanges. Means may be provided at the outgoing end oi the junction line for re-' spending to signaling impulses received froin a local direct current circuit and for transmitting corresponding signals of alternating current over the junction line. At the incoming end of the junction line, means may be provided for receiving the alternating current signals and for sending on the proper signals for operating a further direct cur-' rent circuit which may extend theconnection to the wanted line or to another junction.

These means, conveniently termed alternating current converting circuits, are therefore arra ged at each end of a junction line and according to one feature of theinvention an alternating current converting circuit at the incoming end of the junction. may be, seized fron'i the outgoing end by Ineansof a short pulse of alternating current, 'means being provided whereoy the same OilClllJ can be relea. ed at any time by a long pulse of alternating current, the same groups of relays being used for sending both signals. Y

[Ln alternating current converting circuit may be provided at the incoming end of a junction line which may be so arranged that in response to alternating current pulsesreceived over the unction, it sends out impulses of direct current over the talking wires to operate a direct current circuit and also sends out by-pass impulses over a different wire. Theseby-pa'ss impulses may be received di- 592,490, and in Switzerland January '7, 1931.

rectly in a further alternating current converting circuit which may send on further alternating current impulses over a further junction line. Either or both the line and the by-pass impulses may be received by the second altcrnatin g currentconverting circuit, depending on the path of access, but it both are received only one set of these impulses will be used, the particular set being determined by a discriminating arrangement which may conveniently take the formvof a relay in the second alternating current converting circuit which operates over an addi tional wire on the receipt of the bypass impulses from the preceding converting circuit and disables the relay provided for the receiving of ordinary impulses over the linev wires.

All signals except the release signal may take the form of short pulsesof alternating current which will be sent out fromgthe alternating current converting circuit at the outgoing end of the junction and these signals may be of the same duration. 1

Means may be provided in the alternating current converting circuit for converting these alternating current signals into either dialing pulses or ringing current according to the condition of the direct currentcircuit controlled by the incoming alternating cur.- rent converting circuit.

Backward signals for indicating the progressof the connection may consist ofalternating current pulses of short uniform duration and the arrangement may be such that indicating signals sentback from a direct current circuit at the incoming end of ajunction will produce the usual opening or closing of the fundamental circuit whereupon such signals will be converted by the alternating current converting circuit into alternating current pulses which on being received at the outgoing end will create a corresponding opening and closing of the fundamental circuit at that end. 1

Means may also be provided for insuring that these signals are always kept in the same phase, and that if the frequency at which these impulses are sent becomes too great they are lost in pairs so that the signals still retain the same phase.

An alternating current pulse used for backward signaling is of a specified duration and means may be provided for insuring that this duration shall be the same regardless of the length of the impulse given by a closure or opening of the fundamental produced by the signals given from the direct current circuit. The circuit may be so arranged that if a closure ofthe fundamental is followed veryrapidly by an opening, two alternating current pulses of the correct length are'given and further means may be provided for insuring that;

' the' necessary time elapses between the two ment which renders it insensitive to alternatmg current coming from that direction so that if the circuit is used for signaling in both directions, the alternating current relay so protected is responsive to signals in one direction only.

If two signaling pulses should be transmitted simultaneously in both directions over a junction the first alternating current receiving relay to be operated at either end of the. junction disables the sending relay at that end, thereby arresting the transmission of signaling impulses from that end. Means may be provided, however, whereby these signaling impulses arenot lost but are onlydelayed until a definite interval has elapsed after the pulse in the opposite directio'nhas' been completed.

Means may be provided whereby, if a call should be extended from the outgoing end of the junction to a toll operator at the incoming end and the calling subscriber restore-s,

' a long releasing pulse of alternating current is sent over the junction but the latter is held busy until the. operator disconnects whereupon a backward pulse of alternating current is automatically transmitted over the j unc tion which is thereby released at its outgoing end. Means may be provided whereby if the operator should disconnect before the calling subscriber restores, the backward pulse for releasing the junction is not transmitted until the usual releasing forward pulseis sent in response to the restoration of the calling subscribers receiver.

number of subsidiary exchanges [such as C and mayalso comprise a toll board TB for purposes which will appear hereinafter.

Fig. 2 shows one alternating current w-nverting circuit, such as AC2 adapted to. receive calls from a subscriber in exchange .19; through switch GS and associated circuit AC over line J L. V V

Fig. 3 shows an associated circuit'for extending said calls to an incoming group selector, such as G82.

Fig. 4 shows a both way alternating current converting circuit such as AC3 arranged to receive calls from Fig. 3' through selector GS2 and calls from exchange C over line JL through switch JF or to exchange C over line J L.

Fig. 5 shows. a both, way alternating current converting circuit such as AC4- of exchange C and is arranged to receive calls from Fig. 4 over line JL through switch GS4: to. a desired subscribers line or extend calls over li ne JL to Fig. 4: in the other direction from a local direct current circuit over switch G from a calling subscribers line.

Fig. 5A shows a both way alternating current converting circuit similar to AC4 of exchange C. and is arranged to. receive callsfrom the toll board TB over line JL through switch GSA to a desired subscribers line or extend calls. over line JL? to the toll board TB in the other direction from a local direct current circuit over switch GS5 from a calling subscribers line.

Fig. 6 shows a both way alternating current converting circuit in the toll board TB such as AC5 similar to AC3 Fig. 4 in exchange B and is arranged to receive calls from exchange C over line JL to called subscribers" lines over jack IJ or extend calls over line JL to exchange C in the other direction from a calling subscriber over jack OJ and switch GS6.

Fig. 7 shows how the various figures may be arranged together.

The operation of the arrangement will now be described in a more general manner with reference to Fig. l. 7

'In the case of a call originating in exchange A the connection is extended over the. usual tram of automatic. switches, one of which is represented by GSI, and it the call is for a distant exchange such as B- or C, these switches willextend the connection to the outgoing alternating current converting circuit AC1. This circuit will receive impulses of D. C. current from the callingline; and in-response thereto will transmit a series of A. C. pulses over the .junction line leading to an incoming alter nating current circuit AC2 in exchange B which in response thereto will send out a series of D. G. impulses to a group selector switch such is-G32.

If the connection is destined for a subscriber on the exchange B, it will be extended to the wanted line from the switch GSQ by the usual train of automatic switches (not shown) If, however, the call destined "for a further exchange such as C, the connection will be extended by GSQ to the alternating current converting circuit AC3 which sends an out a series of A; Gimpulses to the alternating current converting circuit AC4 Fig. 5 located in exchange C which will extend the connection to a group selector switch GSA which will in turn extend the connection over the usual automatic switches to the wanted line.

Calls outgoing from exchange C are controlled by registering mechanism in the parent exchange B. To this end, when a 3i) subscriber attached to exchange C removes .his receiver, a junction to exchange B is immediately seized by a hunting switch GS5 and the subscriber becomes connected to a registering mechanism in exchange B over GSB, alternating current converting circuit ACA- Fi 5 alternating current convertingcircuit A03 and a hunting switch'JF.

Should the desired call be destinedfor another subscriber in exchange G means is provided whereby on the receipt of the appropriate dial impulses from the calling subscriber the junction is released and the call is subsequently entirely controlled and established in exchange G.

In certain circumstances when it is not desired to permit the automatic establishment of calls outgoing from exchange C, the latter is associated instead with a toll board TB in the parent exchange B and in order so to permit of ready conversion at a later dateto automatic interconnection the same principles of operation are employed.

Exchange G can. be connected to the toll board TB by means of the both way alter- .ZJ; uating current converting circuit AC4 Fig.

5A which is associated with the circuit AC5.

v When a call is originated by a subscriber in exchange C, a junction to the toll board '3 TB is seized immediately and a connection is extended over J85, AC4 Fig. 5-A and AC 5 to the toll board where a calling lamp is lit only when the appropriate digits have been received after which connection will Gabe completed over the jack Ll. If on the a switch GSA to the wanted line.

circuit AC5 from where it will be extended to the circuit AC4 Fig. 5-A and thence over The circuit operation will now be described in detail.

Referring first to Fig. 2 the circuit is seized by, a short A. C. impulse received over the junction JL on a call from exchange A.

This pulse operates relay D which is tuned to a particular frequency. Relay D closes at all an obvious circuit for relay DD, which operates relayG from ground at (Zdl over ggl and 992. Relay G locks to ground at 92 and operates relay- BA from ground at g1 over 72.1. At the end of the 'A.:C. pulse relays D and DD release and the latter operates the slow releasing relay L Fig. 3: ground, (M2, 93, 72 2, relay L battery. Relay L connects at Z1 over 993 ground to relay GG, Fig. 2 which locks at ggl to .92. Relay Gis now controlled over'ggli, andll. Relay GS closes also a circuit for relay J Fig. 3: ground at brush smb of SM home contact M, 9 996, relay J battery. Relay J closes a circuit for relay AA ground, y'l, brush sons of 8M ha, relay AA battery. Relay AA operates, and'the impulse receiving circuit shown in Fig. 3 is now ready to receive the impulses.

Relay AA closes a circuit for relay H: ground 3'2, cal, 04 1, relay I-l, battery. A circuit is now closed for relay X: ground, 0M2, 93, k3, ml, relay'X, battery. At 022 relay X. transfers the same ground to relay R, which connects the A. C. source AC to the junction J L. Relay H disconnects relay RA and closes at 7A the circuit of relay RE. The releasing time of relay RA determines the length of the back impulse. -The function of relayX is to render relay H independent of rclaysJ and AA during the releasing time of relay RA, so that the back impulse will always e of the same length, ensuring thereby that a correct impulse is given each time relay H has been operated.

' Relay H closed also a circuit for relay S",

Fig. 3, ground, (M2, g3, 7L5, relay S resist-' ance, battery. Relay S closed the circuit for relay E ground, 81, 61, (m2, relay E battery. Relay E looks over aa2, el,-j3 and jl to ground.

The back impulse causes the register of I Each time relay DD opens d012, relay S nulses'rela AA is maintained from round 7. i

at m? O er i1 As soon as the control switchSM had made its first step at the beginning of the impulse train a circuit is closed for the magnet PJ of the selector ground, smb, 3'4, dcl, hcl, magnet PJ battery. The selector starts to chase the switch SM? After the first step of the group selector,it closes its off-normal contact gab. Magnet PJ is now under the control 4 of relay DU and H The selector continues to hunt for a free outlet in the marked group which may lead to a subsequent .A. C. converting circuit, such as AC3, Fig. 4, or to a local circuit. a 7

At the end of the impulse train, relay I falls back, opening at 711 the circuit of relay AA which in turn opens at are?) thecircuit relay of E which de-energizes. At aal relay AA also opens the circuit of relay H, Fig. 2, which releases and a new back impulse (controlled this time by the relay BB) is sent back to the distant register to prevent the transmission of a further impulse train until the next selection.

' As soon as relay I has released at theend of the impulse train acircuit for relay Q is closed: ground, smb, 2'2, relay Q battery. Relay Q transfers at g relay I from the stcp-bystep switch 3M to a resistance and also closes a circuit for relay C ground, (Z61 2, g3, 7L6, roll, e3, 94:, relay C battery.

7 Relay C operates.

WVhen the hunting selector reaches a free outlet in the marked group a circuit is closed for relay H6 battery, terminal 0, re-

lay HC brush and terminal d,' sma, ground at 7'1. Relay HC opens at hcl the circuit of magnet PJiand the selector stops. Relay I-IC introduces the double test relay S0 which operates over g5 and energizes at 861 rela 7 DC?.

'The latter locks to ground at 7'1 and connects at 0Z02ground to the terminal 0. Relay DC closcsthea and 7) wires at (Z03 and (ls l.

A circuit is now closed from ground over relay A 01', (Z03, terminal a, over a high resistance bridge in the subsequent circuit, terminal I), do l, 1, 83, c2, relay B battery. Relays A and B however do not operate as long as the said high resistance bridge is not replaced by a low resistance bridge.

This takes place when the subsequent circuit is ready to receive the next impulse train. Relays A and B then operate and a circuit is closed for relay AA at 61 and a1.

Relay AA pulls up and consequently relays H, S and E operate as described. Relay H causes an impulse to be transmitted back to the distant register which startsto send out the next train of impulses. Relay I is operated on the first release of relay S and maintains relay AA operated during the impulses.

It should be noted that as soon as relay E has been operated relay C remains locked over 03 and 81, so that it falls back on the first impulse. "At 83 relay S opens the 7) wire and retransmits further the opening caused by the first impulse. At the, end of the first impulse relayS is again energized, but at this time ground on the a wire is connected over 04L and battery on the 6 wire over 05.

Relay S remains energized at the end of the impulse train and relay I falls back, opening the circuit of relay AA as described so as to signal to the distant register as before. Relay AA 'opens the circuit of relay E which again operates relay C The circuit is now ready to receive the next train of impulses. The cycle of operations is repeated in the same manner until all selections have been effected. WVhen finally the wanted subscriber replies the supervisory relays A and B o.p-' crate and energize relay AA which operates relay H, and a signal indicating thereply of the'called party is transmitted to the distant exchange. 7 When the calling subscriber releases a long releasing impulse is transmitted from the distant exchange and relays DC and S remain released for the duration of this impulse. Relay L falls back, and so does relay J due to the release of relay G. Relay J 3 opens at jl, the holding circuit of relay DQ which de-energizes and closes at (Z01 the circuit for magnet PJ ground, gsb, (Z01, lwl, magnet PJ battery. The group selector returns to normal where a circuit is closed for the control switch magnet SM ground, smb, 3'5, 8m,

magnet 8M battery. The control switch returns also to normal. 7 It should be noted that if the impulse re ceiving circuit, Fig. 3, is restored before the control. switch regains the normal position, relay J can not be operated since its ground must bereceived over it?) of switch SM Relay L however is independent of the switch 8M and may be operated at any time by the A. C. converting circuit AC2, Fig. 2, and the circuit of Fig. 2 may therefore be seized or released independently of the selector circuit. Referring now to Fig. 4, the following circuit is closed for relay J when the circuit is seized on a call: ground in group selector,

terminal 0, 01, m1 relay J battery, and relay J looks at jl, independently of relay RA. A circuit is also. closed for relay H, relay S ground on the a wire, 02, relay'Ht, 03, to battery on the 6 wire. Relay H energizes relay B ground, rcZl, Z01, Z21, 7'2, relay B battery. Relay B looks at 62 and operates relay RA ground, .723, 661, relay HA battery, and in parallel to relay RA relay RD Z261, W12, W01, relay RD battery. Relay RA opens at m2 the circuit of relay RD, but since relay 7 RA is slow to operate, relay RD finds suflicient time to energize. Belay RD closes the circuit of relay P: ground ?"(Z2, 91, relay P, battery. Relay P connects the A. C. source ACS to the outgoing junction J L1. A short A. C. pulse, the length of which is determined by the releasing time of relay RD is sent out to the distant exchange, for example 0, Fig. 1, to originate therein a call.

When relay RD falls oli" a circuit is closed for relay BB: ground, rcZl, 121, m3, Z262, relay BB, battery and relay BB looks at 653 to m4.

When the distant exchange is ready to recerve a digit, a short pulse is sent back and received by relay D which at 611 operates relay DD over M. Relay DD operates over (ZtZiZ relay AB which lock at abl to 62. Relay AB operates relay S ground, acZl, (r62, re-

lay S to battery on the Z) wire. At the end of the back pulse relays D and DD release, relay DD closing the circuit for relay AD ground, (M1, 81, @63, relay AD battery. Relay AD* locks over ab? to ad2, and connects at (ZZZ3, relay S in bridge across AC3 a" and b wlres, thus giving a slgnal to the preceding circuit and the register respectively to send an impulse train.

In case the circuit has been seized by a local group selector the impulses are received over the a and Z) wires by relay 8*, and in case of an incoming group selector over the 4th wire. In the latter case relay PI is used for sending out'the impulses, this relay being operated in parallel with relay Q, in the following circuit: ground, cZaZl, (Fig. 2), 5/96, Z07, (Z05 (Fig. 3), terminal a of G82, Z964: (Fig. A), (Z64, and from there over cZcZS (Fig. 4) to relay PP and in parallel over 93 to relay Qfi,

which locks over 92 to m l, thereby disabling relay P at 91.

Therefore, when relay S responds to the openings of its circuit in the local circuit, on falling back on each impulse it closesthe circuit of relay P ground, 82, ab5, a014, g4, relay P battery. Relay P connects the A. C. source ACS to the outgoing junction JLl as long as relay S is retracted.

At the end of the impulse train, a short back impulse is received on relay D which operates relayDD At cZcZ2 relay DD shortcircuits relayAB which releases and by opening aZ 2 introduces the high resistance bridge (relay H across the a and Z) wires to prevent the register sending the next train of impulses.

At the end of the back impulse relay D releases followed by relays DD? and AD*.

When the distant circuit is ready, again a further backward impulse is received. Relays AB? and AD are reoperated and the next train of impulses is sent out as before.

Finally the reply of the called party is signaled back to the local link circuit of the originating exchange.

In the case of calls incoming over the junction line J L1 the circuit is seized by a short A. C. pulse received from the distant exchange. The pulse operates relay D which closes a circuit for relay G ground, 6Z1, Z95, ggl, ggQ, relay G battery, and also a circuit for relay C in parallel to relay G from the same ground over ggl, relay C battery; Relay Gr locks at 92 and closes at 91 over jcl and the starting lead SL the starting circuit for the magnet (not shown) of the finder eir cuit J F which starts to hunt for the calling junction. This junction is marked by a battery potential on terminal rZ applied thereto by relay C from battery, 04:, 7'02, terminal 0Z. Relay C disconnects at 01 relay J 4 from the banks of the incoming group selectors in order to make the circuit busy for calls incommg 1n that drrect1on. Relay C also closes a circuit for relay E ground, 2701,

Z61, c5, relay E battery. At the'end of the initiating A. C. pulse, relay D releasesand closes a circuit for relay L ground, d2, 993, 93, relay L battery. circuit for relay GG z ground Z1, 994, relay GGt, battery. Relay GGr locks over gg? to g2, and transfers .at 995 the control of relay Gr torelay L When the finder J F has found the calling line a circuit is closed for relay J C ground at the local link circuit, terminal 0 of J F r'elay' JG, battery. Relay JG opens at jcl the starting lead SL and removes at 7'02 battery potential from terminal (Z. The local link seizes a free register (not shown), and dialing tone is then transmitted to the calling Relay L closes the '3 subscriber. The impulses from the dial switch are converted at the distant exchange into A. G. pulses which are received by relay D* and retransmitted over cZl, b5, 996 to relay 1P which opens at 2702 the loop to the link circuit a corresponding number of times.

Relay 1P on responding to the first pulse alsoreleases relay E and closes at 393 anv obvious circuit for relay LB which'is slow releasing and secures that relay E remains de-energized during the impulse train.

Each digit is received in the same way and transmitted to the register and subsequently all signals from the calling party at the distant exchange are transmitted to the local link circuit. i

WVhen the called party answers, the 6 wire is opened for a short period in the link circuit and relay F t releases. Relay F 4 closes a circuit for relay M ground, cpl, f1, 64, y'03, relay M battery. Relay M closes a circuit for relay P ground, ZZ, m2, n2, g1, relay P battery and an A. G.

pulse is sent to the distant exchange. As'soon as the 6 wire is reclosed relay F re-operates and relay M starts to release. Since, relay M is slow-releasing a circuit will be closed for relay N ground f2, m3, relay Nflbattery. Relay N lock-s at 023, to Z1 and so records that the answering has taken place.

At the end of the conversation, if the called party is first to restore his receiver, the linlr opens the b-wire again and relay M reoperates closing at m2, the circuit of thermostat TH. As soon as the thermostat close-s thl, an A. C. impulse issent to the distant exchange to signal the back release.

' If the calling party hangs up first, a long A. G. pulse is sent out from the distant exchange. Thispulse operate-s relays D and IP as before. Relay 1P opens the loop to the SlOCllfliDk and causes the circuit to release.

On the other hand relay 11 opens the circuitofrelay L which releases and opens at Z1 the circuit of relay G The latter relay releases, but-relay GG remains looked over d1, 94, and 997. At the end of the long pulse relay D releases followed by relay IP andGG and the circuit isagain normal.

Referring now to Fig. 5, if the circuit is taken into use by alocal group selector, such as GSS, ground is connected from the selector circuit (not shown) over the wire W to relay which connects at 61 and '62 relay S in series with the loop, A circuit is also closed for relaysR-A and BB in parallel: ground, 63, relay HA battery, and 63, m1, relay .RD battery. Both relays operate in the same way as, described for Fig. 4 and a short A. 0. pulse is sentover the unction J L1 to the distant exchange by relay P which is energized from ground at rcZl. I

7 It will be assumed here that the junction terminates in an exchange such as exchange B. The said short pulse originates therein. a call. Relay RD on releasing closes a circuit for relay BB ground, M2, Z261, m2, relay BB battery. Relay BB operates. When the register at the distant exchange is ready to receive a digit'o-ver 5L1, the subscriber hears the dial tone and proceeds to send the digits of the required number. For each opening of the dial, relay S releases and closes the circuit for relay P ground, a1, 51, m1, 562, .m3, relayP battery. Relay P operates and connects the A. C. source ACS to the junction. The impulses are then transmitted to the distant register.

When the called party answers a short A. C. pulse is sent back from the distant exchange and is received by relay D which closes the circuit for relay A ground, (Z1, 65, relay A battery. Relay A closes the circuit of relay M z ground, a2, 911, M battery. At the end of the pulse relays D and A restore and a circuit is-closedforrelay N ground, wire W, m1, relay N and M in series, battery. lVhen relay M operated it opened at m2 the b-wire,

which is reclosed at n2 upon relay N operating. The reply 01 the called party is then signaled back to the local circuit.

At the end of the conversation, if the calling party is the first to. replace the receiver relay S releases but nothing happens until ground is removed from relay B Relay B then releases and operates relays BB RG and RD in turn and relay RD operates relay P. A long Ai pulse is sent forward to i the distant exchange to cause the release of the circuit therein.

Relay BB was locked in parallel with relay P and was released at the same moment as relay P Relay BB is slow-releasing to guarantee a definite interval between the long releasing impulse and a new starting impulse, if the circuit has been seized again during the long releasing impulseafter relay RAF has been released.

The relays which are acting for incoming calls are D5, DD, GZGG GA H X5, P and The operation in this case is the same as described for. the circuits of Figs. 2

and 3 and will therefore not bedescribed" again. v

It will be now assumed that the circuit of Fig. 5-1). has access over a junction lineJLZ .to toll operators position TB at a center exchange. Inthis case the operations are very similar to those described in connection withflFig. 5. The operations are as follows:

When the circuit is seizedby a local group selector relays 13 RA and RID? are operatedand a short A. C. pulseis sent ent as before. Relay Reli closes a circu t for relayG Ground m, g1, 62, 991,992, relay G battery, and in parallel thereto for relay Q grounthm l, relay QT, battery. Relay Q5 is slow-operating and thus relay G has time to operate and to lock at 91. Relay Q closes a circuit for relay GG z ground, M1, 2, 2, gg3, relay GG battery. Relay "GG locks at gg l-to g1 and at prepares ailoclzing circuit to (M2. It provides also a locking circuit for relay Q; ground, g1, g t 4,996., 3, relay Q, battery.

If the number dialed by the subscriber is not local, ground is temporarily provided over wires W and VW and relay K and therefore also relay P operate. -A short A. C. pulse is therefore transmitted to the center to light the calling lamp therein.

The position of this circuit remains now unchanged until the end of the conversation are signal the end of the call. The circuit Waits now for a short backward A. C. pulse which is originated from the distant exchange as soon as the toll operator has Withdrawn the plug. This backward A. 0. pulse operates relays D and DD. Relay DD releases relay G but relay GG remains on front contact during the pulse. At the end of the pulse relay D DD GG and Q, release in turn and the circuit is again normal.

Referring now to Fig. 6, the circuit is seized from the distant exchange by a short A. C. pulse which will be sent from the circuit in Fig. 5A. This operates relays D and DD and the latter operates at doll relay G6, which looks and disconnects at g1 relay J from the banks of the group selectors, such as G86, in order to busy the junction JLQ thereat. Belay C operates in parallel with relay G and at 03 relay H is short-circuitcd to provide a supervisory loop through relay S At the end of the A. C. pulse relays D and DD release. lay DD operates at cZd2 relay L which in turn operates relay GG over ZZ and 5/91 and this relay locks under the control of relay G andtransfers at 91 the control of relay G to relay L Relay GG closes at 93 also a holding circuit for relay C. When relay C operated it closed a circuit from the dial tone interrupter DT over 04:, 6.91, primary of dial tone coil DC, battery and dial tone is transmitted to the calling subscriber.

It should be noted that the callinglamp CL I has not yet been displayed. g

If the number dlaled 1s such that the services of the operator are required, a further short A. C. pulse is received. RelayDD op-' crates which operates relay ED. At the end of the pulse relay DD opens the short circuit across relay BS and this relay operates in series with relay Q Relay BS cuts off the dial tone and lights the CL. When a plug is inserted in the jack All, the dial tone coil is disconnected from the line, the lamp CL is extinguished-and a lock ing circuit for relays BS and Q is closed.

At the end of the conversation a long releasing pulse is received. Relay DD operates for a sufiiciently long time to release'relay L which in turn release relay G. At the end of the pulse relay GG" restores and the circuit is again normal with the exception of relays BS Q and RD which are held from the jack. l/Vhen the plug is Withdrawn, re-

lay BS and Q restore. Relay opens the circuit of relay RD", but during the slow circuit release of this relay, relay P operates and sends back a short pulse to release the outgoing end of the junction.

In the case where it is not necessary to call the attention of the operator, i. e., of a local call, a long releasing pulse is received instead of a short one, and while relay BS will operate momentarily during the releasing time of calling lamp relayG-G- the circuit ofthe lamp has already been opend by relay G so that the lamp does not light at all. 7

What is claimed is: I I

1. In a telephone system,a line, meansat one end of said line responsive to direct current signals for conversion into and trans mission of alternating current signals over said line and means at the other end of said line responsive to said alternating current signals for; conversion into and transmission of direct current signals beyond, said last mentioned means being responsive to a preliminary short alternating current signal to prepare it for the reception of succeeding alternatinggcurrent signals for conversion into direct current signals. I

2. in a telephone system, a line, means at one end of the line; for transmitting short alternating current impulses and long alternating current impulses over said line, an alternating current converting circuit at the other end of the line seized in response to a short alternating current impulse received over the line and released inresponse to a long alternating current impulse. received over the line.

3. In a telephone system, aline, a current converting impulse circuit at one end of the line including a plurality of relays operative to seize said converting circuit inresponse to a short alternating current impulse received over said line and effective to release said con verting circuit in response to a long alterhating current impulse received over said.

line.

l. In a telephone system, a current converting circuit means responsive to the reception of direct current signals for transmitting alternating current dialing signals or responsive to the reception of the alternatingcun rent signals for transmitting alternating current ringing signals, means for sewing SL1Cl circuit means and transn'iitting toit direct current signals for conversion into said dialing signals,and means for seizing said circuit means and transmitting to it alternating current, signals for conversion into ringing signals. 7 Y s 5. In a telephone system, a calling subscribersline, an alternating current converh ing outgoing circuit, an alternating current converting incoming circuit, a line between said converting circuits, an operators posi tion, means for establishing a. connection between said' calling-subscribers line and said operators position over said converting cir cuits and connecting line, means responsive to the calling subscriber replacing his receiver on the hook for transmitting a long alternating current'impulse from said out going converting circuit over said connecting line to said incoming converting circuit, and 7 means responsive to said long alternating current impulse and to the operator releasing said established connection for releasing said incoming converting circuit and for transmitting a short alternating current impulse over said connecting line to said outgoing converting circuit, and means responsive to said short alternating current impulse for releasing said outgoing converting circuit. r

6. In a telephone system, a calling subscribers line, an outgoing alternating current converting circuit, an incoming alternating current converting circuit, a line connecting said converting circuits, an operators position, means for establishing aconnection be tween said calling subscribers line and said operators position over said outgoing converting circuit said connecting line and said incoming connecting circuit, means responsive to the calling subscriber hanging up his receiver for transmitting a long alternating current impulse over said connecting line from said outgoing converting circuit to said incoming converting circuit, means responsive to the operator releasing the established connection prior to the calling subscriber hanging up his receiver and to the reception of the long alternating current impulse by said incoming-converting circuits for there after transmitting a short alternating current impulse from said incoming converting circuit over said connecting line to said outgoing converting circuit for releasing said incoming convertingcircuit, and means responsive to the reception of said short alternating current impulse by said outgoing converting circuit for releasing said outgoing converting circuit.

7.111 a telephone system, a calling sub scribers line, an outgoing alternating current converting circuit, an incoming alter nating current converting circuit, a line connecting said converting circuits, an operators position, a signal at said operators position, means for establishing a connection between said calling subscribers line and said operators position over said outgoing converting circuit said connecting line and said incoming converting circuit comprising means for sending alternating current impulses and means responsive to a first alternating current impulse transmitted over the connecting line for seizing the incoming alternating current converting circuit, and means responsive to a second alternating current impulse transmitted over said connecting line for operating said signal at the operators position, means responsive to the calling subscriber hanging up his receiver for transmitting a 7 longer alternating current impulse over said connecting line from said outgoing converting circuit to said incoming converting circuit, means responsive to the operator releasing the established connection prior to the calling subscriber hangingup his receiver and to the reception of the long alternating.

current impulse by Lid incoming converting i: thercaitcr transn ng a short alternat ng current impulse from said iuconr ing converting circuit over said connecting line to said outgoing converting circuit for releasing incoming converting circuit and means 1" -=sponsive to the reception of said last-mentioned short alternating current impulse by said outgoing converting circuit iior releasing said outgoing converting circuit.

8. In a telephone system, a calling subscribcrs line, an outgoing alternating current converting circuit,an incoming alternating current converting circuit, a line connecting said converting circuit, an operators position, a sig al at said opcrators position, means or est-a dishing connection between said calling subscribers line and said operators position over said outgoing converting circuit, said connecting line and said incoming conroot circuit comp "ising means for transmitting an alternating current signal over said connecting line for seizing the incoming alternating converting circuit, means for transmitting a second alternating current im pulse over said connecting line, means responsive to said second alternating current impulse for actuatin said signal at said operatcrs position, means responsive to the sci ing of the incoming alternating converting circuit by the operator for releasing said signal, means responsive When the calling subscriber hangs up his receiver for transmitting a long alternating current impulse over said connecting line om said outgoing convert lllgflliCllll? to said incoming converting circult, means responsive to the operator releasing the established connection prior to the calling subscriber hanging up his receiver and to the reception of the long alternating current iinpulse by said incoming converting circuit for thereafter transmitting a short alternatin current impulse from said inconr ing converting circuit over'said connecting line to said outgoing converting circuit for releasing saidincoming converting circuit,- and means responsive to the receptioinof said short alternating current impulse by said outi converting circuit releasing said outgoing converting circuit.

In Witness WlIQIOf, We hereunto subscribe our names, this 28th day of January, 1932' LESLUE B. HAIGH. HENRI E. A. BOR-ZER. 

